Generally, a tension band for a cathode ray tube is placed tightly around the skirt of the facepanel of the tube to prevent the implosion of the tube. The band functions by restraining the expansion of cracks in the facepanel, which appear when strong pressure or shock is exerted on the facepanel and the high vacuum in the tube causes the violent inward scattering of the tube.
As illustrated in FIGS. 1 and 2, a conventional tension band 10 is made of a metal having a high tensile force, with apertures mounting lugs 20 fixed to the corners of the tension band by welding. The tension band 10 is placed tightly around both the skirt of the facepanel 30, i.e., banding portion 32, and the mold match line between the facepanel 30 and a funnel 40, and drawn up to a very high tension. When the tension band is mounted on the cathode ray tube, an adhesive tape 50 made of heat-resistant material is interposed between the tension band 10 and banding portion 32, so that the tension band 10 is affixed to the skirt of the facepanel 30, being spaced apart from the banding portion 32. When the tension band 10 is tightly placed around the skirt of the facepanel, the adhesive tape 50 is employed to prevent the banding portion 32 from directly contacting the tension band 10 which is subjected to heat, since the banding portion is susceptible to heat. Moreover, while the tension band 10 is affixed to the cathode ray tube or while the tube is undergoing implosion, the smooth-surfaced, metallic tension band is securely fastened by adhesive tape 50 to the predetermined portion without being separated from the banding portion 32 of the cathode ray tube. The adaptation of the tension band 10 minimizes the violent scattering of the facepanel caused by the implosion.
However, the conventional tension band system having the aforesaid structure and the cathode ray tube fastened therewith have problems which will be described below. First of all, the tension band is made of metal with high tensile force and affixed to the tube with insulating adhesive tape. The use of these materials results in a high manufacturing cost. Further, intense heat energy is required to obtain thermal expansion of the metallic tension band needed to place the tension band tightly round the skirt of the facepanel. The use of direct flame to obtain the intense heat results in partial deterioration of the tension band. Such deterioration, in turn, weakens the tensile force of the band. In the structure of the band, an arrangement of precise welding devices is necessary to install the mounting lug, which is made by a separate manufacturing process, at each corner of the tension band. In addition, another separate welding device is needed to prepare the tension band in a loop shape. During the tension band manufacturing processes, rigidly controlled precise welding is required, since the width of the seam portion of the metal band has an ultimate influence on the banding strength obtained around the banding portion of the cathode ray tube.